ENYO-4061: RangeSlider throws initialization error.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>
Merge pull request #209 from enyojs/ENYO-4061-aarontam

ENYO-4061: RangeSlider throws initialization error.

Reviewed by: Roy Sutton <roy.sutton@lge.com>